肖建彬的博客

作者: 肖建彬 | 可以转载, 转载时务必以超链接形式标明文章原始出处和作者信息及版权声明
网址：http://www.xiaojb.com/archives/mailtech/32_or_64_bit.shtml

With Postfix, you need 64 bits if you plan to manipulate messages
or mailbox files larger than 2GB; it should not make a difference
for performance unless you do lots of content manipulation.

The 2GB is for very lame but also very pragmatic reasons. Postfix
prefers to use signed numbers internally for buffer etc. sizes,
because it is much easier to write robust code than with unsigned
numbers. When a signed number overflows you get a negative object
size, which is easy to catch. When an unsigned number overflows
you get a small number, and that can’t raise alarms by itself.